Whoa, slow down. A few things to verify here before we assume the account is banned:

Check the e-mail address. Verify it ends in battle.net or blizzard.com. This is easily faked, but it's a good first precautuon.

The URL. Does it send you to a legitimate battle.net or worldofwarcraft.com address? Double check in your browser.

The content of the e-mail. Blizzard wouldn't give you X amount of time to reply before taking action. They would do it and then e-mail you.

Double check all this again and submit a ticket on battle.net to verify the legitimacy of the message. You may have just fallen for a phishing scam and given someone else your account details. I would go directly to battle.net asap and change your password. If you don't have an authenticator on your account, now's a good time to do so. Keep a close eye on your account as well if you're still able to log in to the game.

Your best bet is to actually visit the site by typing in the address instead of clicking a link in the email. Email addresses can be masked in the same way that you should be semi-skeptical about emails from banks.

If actually log in to your battle.net account then your account status should be listed on your game account.